What is Fragile X Syndrome primarily characterized by?

• A. Autosomal recessive inheritance
• B. Environmental causes leading to cognitive decline
• C. Repeating codon sequences affecting mental and physical development
• D. Excessive dopamine levels in the brain

Answer: (C)

Fragile X Syndrome is primarily characterized by repeating codon sequences, specifically a trinucleotide repeat (CGG) in the FMR1 gene located on the X chromosome. This genetic mutation leads to the silencing of the gene, which is responsible for producing a protein critical for normal brain development and function. The resulting deficiency in this protein disrupts neural connections, ultimately affecting mental and physical development. Individuals with Fragile X Syndrome often experience developmental delays, intellectual disabilities, social anxiety, and various behavioral issues.

The other choices are not accurate representations of Fragile X Syndrome. The syndrome does not follow an autosomal recessive pattern; instead, it is X-linked. Environmental causes are also not the primary factor; rather, it is the genetic mutation that drives the condition. Lastly, while dopamine levels do influence various neurological and psychiatric conditions, elevated dopamine is not a characteristic of Fragile X Syndrome. The defining feature is indeed the repeating codons in the FMR1 gene, which have a direct impact on cognitive and physical development.